MSK Cortex Biochemistry Flashcards
What level of bone mineral density means someone has osteoporosis?
Less than 2.5 standard deviations below the mean peak value of young adults of the same race and sex
What level of bone mineral density means someone has osteopenia?
Between 1 to 2.5 standard deviations below mean peak value
What is type 1 osteoporosis?
Post‐Menopausal Osteoporosis with an exacerbated loss of bone in the post‐menopausal period
What are the risk factors for type 1 osteoporosis?
Early menopause Smoking Alcohol abuse Lack of exercise Poor diet
Which fractures tend to occur in people with type 1 osteoporosis?
Colles fractures and vertebral insufficiency fractures
What is type 2 osteoporosis?
Osteoporosis of old age with a greater decline in bone mineral density than expected
What are the risk factors for type 2 osteoporosis?
Similar to type 1 plus:
Chronic disease
Inactivity
Reduced sunlight exposure (Vitamin D)
Which fractures tend to occur in people with type 2 osteoporosis?
Femoral neck fractures and vertebral fractures
What can osteoporosis occur secondary to?
Corticosteroid use, alcohol abuse, malnutrition, chronic disease (CKD, malignancy, Rheumatoid arthritis) and endocrine disorders (Cushing’s, Hyperthyroidism, Hyperparathyroidism)
How is osteoporosis diagnosed?
DEXA scan
In osteoporosis are the levels of serum calcium and phosphate high/low/normal?
Normal
What pharmacological treatments are used to try to prevent fragility fractures?
Calcium Vitamin D supplements Bisphosphonates Desunomab Strontium
What is osteomalacia?
Abnormal softening of the bone - due to deficient mineralization of osteoid (immature bone) secondary to inadequate amounts of calcium and phosphorus
What are symptoms of hypocalcaemia?
Paraesthesiae, muscle cramps, irritability, fatigue, seizures, brittle nails
In osteomalacia what are the levels of calcium, phosphate and serum alkaline phosphatase like?
Calcium - low
Phosphate - low
Alkaline phosphatase - high
What does the treatment of osteomalacia involve?
Vitamin D therapy with calcium and phosphate supplementation
What can cause primary hyperparathyroidism?
Benign adenoma
Hyperplasia
Malignant neoplasia (rare)
What does an overproduction of PTH result in?
Hypercalcaemia with subsequent symptoms and signs (fatigue, depression, bone pain, myalgia, nausea, thirst, polyuria, renal stones, osteoporosis)
In hyperparathyroidism what are the levels of serum PTH, calcium and phosphate?
Serum PTH - high
Calcium - high
Phosphate - normal/low
What is secondary hyperparathyroidism?
A physiological overproduction of PTH secondary to hypocalcaemia usually caused by vitamin D deficiency or CKD
What is tertiary hyperparathyroidism?
Patients with chronic secondary hyperparathyroidism (usually CKD) who develop an adenoma which will continue to produce PTH despite biochemical correction
What is Paget’s disease?
Chronic disorder which results in thickened, brittle and mis‐shapen bones
What could be the aetiology of Paget’s disease?
Viral infection (paramyxoviruses) and genetic defects
Why does Paget’s disease cause brittle bones which are prone to fracture?
Increased osteoclast activity causes an increase in osteoblast activity to counteract this however the new bone fails to remodel sufficiently and so despite it’s thickness and density the new bone is brittle and can fracture easily
In Paget’s disease what are the levels of calcium, phosphate and alkaline phosphatase like?
Calcium - normal
Phosphate - normal
Alkaline phosphatase - high
What is the treatment of Paget’s disease?
Bisphosphonates (which inhibit osteoclasts) or calcitonin if extensive lytic disease. Joint replacement may be necessary and pathological femoral fractures should be stabilised with long intramedullary nails or plates
